A storage system is a computer that provides storage service relating to the organization of information on writeable persistent storage devices, such as memories, tapes or disks. The storage system is commonly deployed within a storage area network (SAN) or a network attached storage (NAS) environment. When used within a NAS environment, the storage system may be embodied as a file server including a storage operating system that implements a file system to logically organize the information as a hierarchical structure of directories and files on, e.g. the disks. Each “on-disk” file may be implemented as a set of data structures, e.g., disk blocks, configured to store information, such as the actual data for the file. A directory, on the other hand, may be implemented as a specially formatted file in which information about other files and directories are stored.
The file server, or filer, may be further configured to operate according to a client/server model of information delivery to thereby allow many client systems (clients) to access shared resources, such as files, stored on the filer. Sharing of files is a hallmark of a NAS system, which is enabled because of semantic level access to files and file systems. Storage of information on a NAS system is typically deployed over a computer network comprising a geographically distributed collection of interconnected communication links, such as Ethernet, that allow clients to remotely access the information (files) stored on the file server. The clients typically communicate with the filer by exchanging discrete frames or packets of data according to pre-defined protocols, such as the well-known Transmission Control Protocol/Internet Protocol (TCP/IP).
In the client/server model, the client may comprise an application executing on a computer that “connects” to the filer over a computer network, such as a point-to-point link, shared local area network, wide area network or virtual private network implemented over a public network, such as the well-known Internet. NAS systems generally utilize file-based access protocols; therefore, each client may request the services of the filer by issuing file system protocol messages (in the form of packets) to the file system over the network. By supporting a plurality of file system protocols, such as the conventional Common Internet File System (CIFS), the Network File System (NFS) and the Direct Access File System (DAFS) protocols, the utility of the filer may be enhanced for networking clients.
Conversely, a SAN is a high-speed network that enables establishment of direct connections between a storage system and its storage devices. The SAN may thus be viewed as an extension to a storage bus and, as such, a storage operating system of the storage system enables access to stored information using block-based access protocols over the “extended bus.” In this context, the extended bus is typically embodied as Fibre Channel (FC) or Ethernet media adapted to operate with block access protocols, such as Small Computer Systems Interface (SCSI) protocol encapsulation over FC (FCP) or TCP/IP/Ethernet (iSCSI). A SAN arrangement or deployment allows decoupling of storage from the storage system, such as an application server, and some level of storage sharing at the application server level. There are, however, environments wherein a SAN is dedicated to a single server.
A storage system typically includes a large amount of storage (e.g., 6 terabytes) with the ability to support many (thousands) of users. This type of storage system is generally too large and expensive for many applications or “purposes.” Even a typical minimum storage size of a volume (or file system) is approximately 150 gigabytes (GB), which is still generally too large for most purposes. Rather than utilizing a single typical storage system, a user may purchase a plurality of smaller servers, wherein each server is directed to accommodating a particular purpose of the user. However, there is still the granularity of storage issue since, as noted, the typical minimum storage size of a volume is approximately 150 GB. In addition, the acquisition of many smaller servers may be more costly than the purchase of a single storage system. Furthermore, the cost of maintenance and administration of many smaller servers is typically substantially more than the cost of maintaining and administering a single storage system. Therefore, it would be desirable to consolidate many servers within a single filer platform in a manner that logically embodies those servers. Server consolidation is thus defined as the ability to provide multiple logical or virtual servers within a single physical server platform. Examples of virtual servers that may be embodied within a single platform are web servers, database servers, mail servers and name servers.
Previous techniques for server consolidation permitted a plurality of virtual instantiations of a server to execute on a single physical server platform. However, such instantiations were limited to file-based protocols, such as the Network File System (NFS) or the Common Internet File System (CIFS). Such consolidated servers were not capable of processing SAN-based data access requests utilizing block-based protocols, such as FCP or iSCSI. As a result, administrators desiring to utilize server or consolidated servers were limited to NAS-based networks utilizing file-level protocols. However, administrators desiring to utilize block-based protocols were required to acquire separate servers or a plurality of physical servers to meet their data access needs. This requirement is often uneconomical due to the large minimum storage size of a volume. As such, administrators establishing SAN-based systems often utilize only a small portion of the minimum required storage space, thereby “wasting” a large percentage of the purchased storage capacity.